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排序方式: 共有1016条查询结果,搜索用时 4 毫秒
121.
Nadia H. Khiadani Sayed Mostafa Safavi Hemami Faramarz Hendessi 《Wireless Personal Communications》2014,77(2):991-1006
Mobility models of nodes have an important role in the evaluation of data dissemination protocols in vehicular ad hoc networks (VANETs). Many recent researches have used the constant velocity mobility models while vehicles have acceleration and their speeds change as they move. Because of the dynamic nature of VANETs, the network changes from a densely connected to the sparsely connected environment in a short time. In sparsely connected networks, it is said that vehicles move in clusters. In this paper, the constant acceleration mobility calculations for the sparsely connected network and its characteristics have been presented. These characteristics are usable for the evaluation of the data dissemination protocols in VANETs. The results show that acceleration affects the number of viewed clusters during the trip and the number of vehicles within a cluster. In fact, acceleration has a significant impact on the network sparsely connection. This matter shows that the appropriate data dissemination protocol should be used to study the acceleration effect which is applicable in sparse networks. The analysis in this research provides the necessary background for better understanding and accurate calculations for the evaluation of data dissemination in VANETs. 相似文献
122.
Although Tunisian winters are mild compared with northern regions, there are heating requirements; their limited level suggests that passive solar energy would probably be able to meet them. However, the summer is hot enough, and one may wonder whether a solar design oriented toward the cold season would not induce severe overheating. Numerous studies have dealt with the heating performance of passive solar elements, but very little has been done to analyze their behavior in hot climatic conditions. The National School for Engineers of Tunis has built a passive solar pavilion which has been carefully instrumented. Special care has been devoted to the summer behavior of the pavilion. In this paper we describe some of the actions taken to prevent overheating, and we investigate their efficacy both by analysis of recorded measurements and by simulation. It is found that night ventilation is the most responsible action in decreasing room temperature, and that Trombe wall screening is more efficient than operating the walls as a solar chimney; overhangs are of valuable aid, and shuttering of the direct gain element also helps against overheating. The high thermal capacity results in a very stable room temperature, and plays an essential role for cooling when coupled with night ventilation. Finally, it is found that if appropriate action is taken in the hot season, a house equipped with passive solar heating elements can reach a very acceptable level of comfort in summer time. 相似文献
123.
Identification and chemical characterization of specific organic indicators in the effluents from chemical production sites 总被引:1,自引:0,他引:1
The structural diversity of the wastewater composition was described by the use of detailed non-target screening analyses of industrial effluents from chemical production sites. Determination of the indicative organic compounds acting as potential molecular indicators for industrial emissions from chemical production industries has been possible due to (i) detailed characterisation of industrial contaminants and identification of compounds with high source specificity, (ii) quantitative determination of the organic constituents in the industrial effluents and (iii) the review of their industrial applications. The determination of potential site-specific markers and industrial molecular indicators corresponding to certain production processes (production of starting materials for manufacturing paper and printing inks, powder coatings as well as epichlorohydrin production) was performed in this work.The results of this study allowed significant contributions to the chemical characterisation of industrial contaminants and isolation of indicators that can act as representatives of industrial effluents in the aquatic environment. 相似文献
124.
Reham Hammad Reda Badr Aglan Shaymaa A. Mohammed Eman Abu-elnasr Awad Marwa A. Elsaid Hanan M. Bedair Seham K. Khirala Mohamed A Selim Asmaa A. Abo Elqasem Areej Rushdi Mohamed Ali Omaima I. Abo-Elkheir Eman F. Sanad Nadia M. Hamdy 《International journal of molecular sciences》2022,23(20)
Virus-related hepatocellular carcinoma (HCC) pathogenesis involves liver inflammation, therefore, despite successful treatment, hepatitis C virus (HCV) may progress to HCC from initiated liver cirrhosis. Cytotoxic T cells (Tcs) are known to be involved in HCV-related cirrhotic complications and HCC pathogenesis. The inhibitory checkpoint leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1) is expressed on Tcs. Therefore, we aimed to determine whether the Tc expression level of LAIR-1 is associated with HCC progression and to evaluate LAIR-1 expression as a noninvasive biomarker for HCC progression in the context of liver cirrhosis related to HCV genotype 4 (G4) in Egyptian patients’ peripheral venous blood liquid biopsy. A total of 64 patients with HCC and 37 patients with liver cirrhosis were enrolled in this case-controlled study, and their LAIR-1 expression on Tc related to the progression of liver cirrhosis was examined and compared to that of the apparently healthy control group (n = 20). LAIR-1 expression was analyzed using flow cytometry. Results: The HCC group had significantly higher LAIR-1 expression on Tc and percentage of Tc positive for LAIR-1 (LAIR-1+Tc%) than the HCV G4-related liver cirrhosis group. LAIR-1+Tc% was correlated with the HCC surrogate tumor marker AFP (r = 0.367, p = 0.001) and insulin resistance and inflammation prognostic ratios/indices. A receiver operating characteristic (ROC) curve revealed that adding LAIR-1+Tc% to AFP can distinguish HCC transformation in the Egyptian patients’ cohort. Upregulated LAIR-1 expression on Tc could be a potential screening noninvasive molecular marker for chronic inflammatory HCV G4 related liver cirrhosis. Moreover, LAIR-1 expression on Tc may be one of the players involved in the progression of liver cirrhosis to HCC. 相似文献
125.
Magdy W. Sabaa Nadia A. Mohamed Riham R. Mohamed Soliman M. Abd El Latif 《Polymer Bulletin》2011,67(4):693-707
A novel super absorbent polymer was prepared by graft copolymerization of 4-vinyl pyridine (4VP) onto the chains of carboxymethyl
chitosan in aqueous solution using potassium persulphate (KPS) as initiator. The effect of monomer and initiator concentration,
reaction temperature, and time on the grafting yield has been investigated. The maximum grafting yield was achieved at [KPS] = 4 × 10−2 mol/L, [M] = 2.5 mol/L at reaction temperature = 60 °C within reaction time = 3 h. The molecular structure of the graft copolymer
was confirmed by FTIR, surface morphology before and after the polymerization was examined by SEM. Different analyses were
done for the graft copolymer such as X-ray diffraction, solubility tests, and thermal analysis. Different applications were
done on the graft copolymer such as swell ability in different pH solutions, dye, and metal uptake. 相似文献
126.
Elder John P.; Ayala Guadalupe X.; Campbell Nadia R.; Slymen Donald; Lopez-Madurga Eva T.; Engelberg Moshe; Baquero Barbara 《Canadian Metallurgical Quarterly》2005,24(1):49
Participants (N = 357) were randomly assigned to 1 of 3 conditions: lay health advisor (promotora) plus tailored print materials, tailored print materials only (tailored), or off-the-shelf print materials (control). The primary outcomes were calories from fat and daily grams of fiber. Secondary outcomes included total energy intake, total and saturated fat intake, and total carbohydrates. Adjusted for baseline values, calories from fat were 29%, 30%, and 30% for the promotora, tailored, and control conditions, respectively, and grams of fiber consumed were 16 g, 17 g, and 16 g. Significant Condition X Time interactions were not observed between baseline and 12-weeks postintervention. The LHA condition achieved significantly lower levels of energy intake, total fat and saturated fat, and total carbohydrates. The relative superiority of the promotora condition may derive from the personal touch achieved in the face-to-face interactions or from the women's use of print materials under the promotora's guidance. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
127.
Nadia Maïzi 《Systems & Control Letters》1994,22(6):457-465
We present an approach to the problem of finding an L∞ approximant of the infinite-dimensional system describing the diffusion of heat in a wall. We show that this system can be regarded as a delay system with Laplace variable √s. We are able to get results, established in Zwart et al. (1988), about partial fraction expansion for delay systems, achieved by some adjustment to the specificities of our particular case. The determination of an L∞ approximant is realised in two steps, using the optimal Hankel-norm approximation. 相似文献
128.
Efficient self-collision detection on smoothly discretized surface animations using geometrical shape regularity 总被引:6,自引:0,他引:6
We present a new algorithm for detecting self-collisionson highly discretized moving polygonal surfaces. If is based on geometrical shape regularity properties that permit avoiding many useless collision tests. We use an improved hierarchical representation of our surface that, besides the optimizations inherent to hierarchisation, allows us to fake adjacency information to our advantage for applying efficiently our geometrical optimizations. We reduce the computation time between each frame by building automatically the hierarchical structure once as a preprocessing task. We describe the main principles of our algorithm, followed by some performance tests. 相似文献
129.
130.
The paper is concerned with simulating the macroeconomic adjustment processes arising in a small open economy experiencing a temporary period of oil production. In a recent paper, Harvie conducted a similar exercise for an economy in which the spending effect arising from such oil production dominated the resource movement effect. That paper concluded that the wage adjustment processes operative were important in influencing the macroeconomic adjustment process arising. Specifically, that paper concluded that wage indexation was preferable during the period of oil production, but that de-indexation was preferable in the post oil production period. Although, in the present paper, the principles underlying the simulated model are the same as in Harvie, the emphasis here is placed on the resource movement consequences arising from temporary oil production. The major conclusion identified is that wages policy is still important in influencing the macroeconomic adjustment processes identified. However, a difference arises not in regard to the profile of that adjustment but rather in its magnitude. The paper emphasizes, in particular, developments in non-oil output, consumer prices, and the stock of domestically held foreign assets. The simulation results suggest that, where the resource movement effect dominates, it would be preferable to de-index wages during the period of oil production and index wages in the post oil production period. Hence wages policy should be regarded as an important component of a government's policy response arising from a period of temporary oil production, irrespective of whether the resource movement or spending effect dominates. However, what that policy response should be would depend on the relative importance of either effect. 相似文献